1. Field of the Invention
The present invention relates to a liquid ejection volume control apparatus and method, a program and an inkjet apparatus, and more particularly, to control technology for adjusting a liquid ejection volume in a liquid ejection head having a plurality of liquid ejection ports (nozzles) to an appropriate volume.
2. Description of the Related Art
In an inkjet printing apparatus which forms an image on a recording medium by ejecting ink from a plurality of nozzles, density non-uniformities (density irregularities) are liable to occur in a recorded image due to variation in the ejection characteristics of respective nozzles of the recording head (inkjet head). As a device for correcting these density non-uniformities, a density correction value is determined for each nozzle from the ejection characteristics of each nozzle, and ejection of inks from the respective nozzles is controlled by correcting the image signal in accordance with the correction values (Japanese Patent Application Publication Nos. 2005-205711 and 2009-234115).
For example, in order to ascertain the ejection characteristics of each nozzle in the nozzle row of a recording head, a test chart for density measurement is formed on a recording medium and the optical density of the test chart is measured. Output density correction values are calculated for each nozzle position on the basis of these measurement results, and the input image signal is corrected on the basis of the calculated correction values.
In the case of an inkjet printing apparatus which includes a plurality of recording heads corresponding to each of a plurality of ink colors (for example, cyan, magenta, yellow, black), a correction lookup table (LUT) which specifies a conversion coefficient between an input signal value and an output signal value is required for each nozzle of a plurality of heads, and therefore the data volume of this group of LUTs is enormous. In particular, in the case of a recording head based on a single-pass method which can record over the full width range of the image forming region of the recording medium by one relative movement, the number of nozzles in each head is large, and therefore the data volume of the correction LUT is of the order of 100 MB.
In actual image recording (printing), it is necessary to adjust the ink volume to an appropriate ink volume for each type of paper, and therefore an operation of adjusting the ink ejection volume is carried out before printing. In this case, if the ink ejection volume is calculated by accessing the correction LUT of each nozzle, then there is a problem in that the calculation time becomes long.
A problem of this kind is not limited to an inkjet printing apparatus, and is common to systems which form various types of patterns using a liquid ejection head based on an inkjet method (for example, a wiring image formation apparatus, a fine structure forming apparatus, or the like).